The present invention relates to a system for providing individual supplementary subscriber services in a cellular mobile communications network, and more particularly to the use of a home location register for implementing individual supplementary subscriber services in a cellular mobile communications network.
A primary characteristic of a mobile communications system, such as a cellular telephone system, is the fact that subscribers to the system may move around. Accordingly, such systems are typically realized as a network of neighboring radio cells which together provide complete coverage of the area to be serviced. Each cell has a Base Station (BS) operating on a set of radio channels. The set of radio channels assigned to a given cell is different from the channels used in neighboring cells in order to avoid interference. A group of BS's is controlled by a Mobile services Switching Center (MSC), which controls calls to and from the Public Switched Telephone Network (PSTN), Integrated Services Digital Network (ISDN), and Public Land Mobile Network (PLMN). In a cellular telephone system, the role of the MSC is equivalent to that of the local exchange in the fixed network. That is, the MSC is responsible for handling tasks such as switching, routing and charging.
It is desirable to provide a mobile subscriber with a uniform set of services that he can use independent not only of his current location, but also independent of which operator is serving his current location. For this reason, well-known cellular systems such as the Nordic Mobile Telephone System (NMT), the Total Access Communication System (TACS), Advanced Mobile Phone System (AMPS), American Digital Cellular System (ADC), the Global System for Mobile Communication (GSM), and the Pacific Digital Cellular System (PDC) have all adopted standardized techniques for providing both basic as well as supplementary services to a roaming subscriber. As used in this specification, the term "basic service" refers to the ability of a communication network to simply establish a call. The term "basic service" will also refer here to those services, such as three party calling, which are available to all subscribers without requiring an individual subscription to a service. In contrast, the term "supplementary service" refers to all of those capabilities, in mobile as well as fixed networks, which go beyond those services which are considered "basic", and which do require an individual subscription before that service can be invoked. Individual supplementary subscriber services may be divided into two types: those which modify or supplement the process of originating a call (referred to here as "A-subscriber services"), and those which modify or supplement the process of terminating (i.e., receiving) a call, referred to here as "B-subscriber services"). A-subscriber services include, but are not limited to: barring of outgoing calls, and private numbering plans. B-subscriber services may be broken down into those which are invoked unconditionally, regardless of the status of the called subscriber or the network, and those whose invocation depends on a particular status or condition being present at the subscriber or in the network. Unconditional B-subscriber services include, but are not limited to: barring of incoming calls; call forwarding, unconditional. Conditional B-subscriber services include: call forwarding on busy; call forwarding on no reply; call forwarding on congestion; and call waiting. The operations and implementations of such cellular systems are well known in the art, and described in numerous publications. For example, the GSM standard is described as part of the ETSI standard. GSM specifications 02.82-02.89, 03.81-03.90, 04.10, and 04.80-04.90 are hereby incorporated by reference. ADC is based on the IS-54 standard. A detailed description of any of these well-known systems is beyond the scope of the present discussion. However, features of these systems which are pertinent to the present invention will be briefly outlined below.
In order to be able to place a call which terminates at a mobile station (MS) whose whereabouts may be continually changing, a data base is required in the network for keeping track of a particular MS. The above cellular systems have adopted the use of a data base called the Home Location Register (HLR), which is implemented as a node in the mobile radio communication network. The HLR for use in GSM is described in GSM specifications 09.02, 03.12 and 03.08, which are hereby incorporated by reference. When someone subscribes to receive service from an operator, such as any of the ones mentioned above, his subscription is entered in the HLR of that operator. The HLR contains subscriber information, such as supplementary services. Furthermore, the HLR stores information about the location of the MS, which information identifies the MSC serving the present location of the MS. This information is updated as the MS moves around by having the MS send location information to its HLR by means of an MSC.
Thus, when an MS roams into a new MSC area, it registers with that MSC, which in turn requests data about the MS from the HLR. At the same time, the HLR is informed of which MSC area the MS is presently located in. If, later on, the MS wants to make a call, the MSC will already have the information needed for the call set-up without having to interrogate the HLR each time.
In addition to basic subscriber services, individual supplementary subscriber services may also be supported. As mentioned above, these include, for example, call forwarding on busy, and private numbering plans (i.e., the MS's use of a personally selected "short number" for placing a call to a recipient whose full number is known and used by the system). The HLR typically plays a part in managing individual supplementary subscriber services in that, in addition to storing the present location of a roaming subscriber as described above, the HLR may also store subscriber categories and call forwarding numbers. The HLR updates subscriber category information and forwarding numbers (i.e., "C-numbers") in its memory when requested to do so by an authorized terminal (i.e., a terminal in the wirebound network with the associated subscription number, or a mobile radio terminal which has authenticated itself as the subscriber terminal). The HLR transmits selected parts of this information to an interrogating MSC on the occasion of registration of a roaming MS, and to a gateway MSC (GMSC) on the occasion of MS-terminated calls as explained in more detail below. However, no information is transmitted to an MSC merely because an MS is originating the call (e.g., a mobile station calling a wirebound subscriber).
In a typical network, then, A-subscriber services and conditional B-subscriber services are provided by the MSC, based on the subscriber categories provided to the VMSC by the HLR at the time of registration. There is no need for the MSC to again contact the HLR at the time of call setup. Also, in the prior art, the HLR is not capable of making conditional decisions because the standardized MSC-HLR interface does not include the ability to report subscriber status (e.g., busy, no answer, etc.) to the HLR, nor does it allow the conveyance of commands depending on such input. By contrast, unconditional B-subscriber services are invoked by the HLR because a call to a mobile subscriber always means that the first MSC contacted (i.e., the GMSC) will consult the HLR in order to learn the whereabouts of the subscriber. At this time, the HLR is in the best position to handle unconditional services such as barring an incoming call, or sending to the GMSC the C-number to which the call is to be unconditionally forwarded.
In order to standardize the means of communication between an HLR and an MSC, cellular communications systems have adopted the use of the Mobile Application Part (MAP) of the communications protocol known as CCITT Signaling System No. 7. Recommendations Q.701-707, Q.711-714 and Q.771-775 in CCITT's "Blue Book" are hereby incorporated by reference. There are different variants of the MAP protocols for use with correspondingly different cellular standards (GSM, ADC, PDC, etc.).
As new supplementary services are developed, it is necessary to be able to quickly incorporate them into existing mobile and non-mobile (i.e. "fixed") communications networks. In fixed networks, rapid service development is achieved by the use of a network definition known as Intelligent Network (IN). The idea of IN is to provide intelligent nodes in the network which may be consulted by other nodes in the network and updated from other nodes. Intelligent nodes consist of data processing equipment connected to other nodes only via data links for signaling. Intelligent nodes do not have switched user connections for speech or for user data transfer. Consequently, they may be accessed via data links only from particular other nodes in the network, such as service switching points (SSPs) in the PSTN. In accordance with the IN concept of functional entities, new services are introduced by adding new program modules in the IN-nodes, each corresponding to an IN functional entity. For example, a services control point (SCP) is the node in the network where most of the service logic resides. A services switching point (SSP), as described above, is the node that handles the switching functions necessary to enable the services invoked by the SCP.
These nodes correspond to functional entities which have been defined by the IN standards presented in CCITT Recommendation Q.1218, which is hereby incorporated by reference. The SCP is the hardware node corresponding to the service control function (SCF), and the SSP is the hardware node corresponding to the service switching function (SSF). Another function, the service data function (SDF), is also implemented in the SCP. It stores the service data needed for the SCF. Communication between the SSF and the SCF (and therefore, between the SSP and the SCP) is by means of a protocol called the Intelligent Network Application Part (INAP), which is also an application on CCITT no. 7.
The use of the IN network addresses the problem of how to rapidly implement new supplementary services in a fixed network. However, the IN network has been developed without consideration for the problem of how to provide these same new supplementary services in a cellular environment, in which subscribers are mobile. As a result, a number of proprietary solutions for use in the cellular environment now exist, producing a situation in which some supplementary services are implemented in the HLR, and other services are implemented in the SCP. Furthermore, management and implementation of most supplementary services within the cellular environment is distributed between the MSC and the HLR.
This approach impedes the rapid development of new services because the introduction of a supplementary service often not only requires a change to the HLR for management of the service and a change to the MSC for invocation of the service, but it also often requires a modification of the MAP protocol between the HLR and the MSC in order to permit the transferring of the supplementary services data between the HLR and the MSC. Consequently, the introduction of supplementary services in a cellular system requires a very long lead time, due to the number of nodes that must be updated with new software, and the fact that the operator usually wants the new service to be available throughout the entire network before being offered to the subscribers, so that all MSC's in the network must be updated before a new service is offered to the mobile subscribers.
As mentioned above, the IN solutions in the fixed network environment achieve rapid introduction of new services as a result of the functional division between the SCF and the SSF, in which the complete individual service logic resides in the SCF, and the SSF only performs generic switching functions (e.g., monitor and report call events, set up new leg, disconnect leg) under the direction of the SCF. However, the IN solution cannot also be applied to the cellular environment because there is a conflict between the operation strategies of the SCF and the HLR, the SDF and the HLR and the SSF and the MSC. That is, the SCF performs the same functions as the HLR, but it uses a different implementation and different interfaces. The same may be said of the relationship between the SDF and the HLR, as well as between the SSF and the MSC. For example, the SCF is meant to control all services in an intelligent network. However, this arrangement is violated by the cellular standards which always require that the HLR contain the information that is necessary for invoking a number of services, such as call forwarding unconditional and barring of incoming calls. Similarly, in the intelligent network the SDF serves as the data storage function for the subscriber, whereas subscriber data in a cellular network is always stored in the HLR.
For coordinating services between the mobile network and the fixed network, there exist only the switched connections between the PSTN and the PLMN, i.e., between the End Office/Tandem (EO/T), which is a unit in the PSTN, and the MSC which is the corresponding unit in the PLMN. The EO/T has an interface to the SCP which stores vital service information for the PSTN subscribers. Similarly, as described above, the MSC has an interface to the HLR which stores location and service information for the PLMN subscribers. According to the present state of the art, the PSTN cannot access the HLR and the PLMN cannot access the SCP. Consequently, if a subscriber requests a service that is available in the other network but not in his own, providing this service is only possible by routing the call to the other network, because signaling associated with these services is not provided between the networks.
To illustrate the solutions presently being applied to provide supplementary services to mobile subscribers, two examples will now be presented. The first of these examples will explain how the supplementary service known as "call forwarding on busy" has been implemented in the prior art. The purpose of the "call forwarding on busy" service is to allow a called subscriber to designate an alternative number which will terminate an incoming call in the event that the subscriber's primary number is already in use (i.e., busy). The following description, then, serves as an example of the prior art implementation of a supplementary service which supplements the ability to terminate a call. It will now be described with reference to FIGS. 1 and 2.
In step 201 a wirebound subscriber 101 (A=originating subscriber) calls a cellular subscriber 103 (B=called subscriber), and the call is set up from the calling subscriber to MSC1 104 through connection 105, PSTN 109, connection 106. It will be recognized that, in this example, the calling subscriber could alternatively be a cellular radio subscriber 102. However, for the remainder of this description, reference will be made only to the wirebound subscriber 101.
In step 202 the MSC1 104 utilizes the MAP-interface 108 to ask the HLR 107 about the present location of cellular subscriber 103 and gets back the cellular subscriber's roaming number.
In step 203 the MSC1 104 uses the roaming number to route the call to the cellular subscriber 103 via connection 111, PSTN 109, connection 112 and MSC2 113.
In step 204, MSC2 113 detects that the called cellular subscriber 103 is busy. In response, logic means within the MSC2 113 cause it to read in its category store (which was updated via MAP-interface 117 when the B subscriber roamed to the region of MSC2) that this particular called subscriber has "call forwarding on busy" to a particular C number given in the store.
In response to this determination, the MSC2 113, in step 205, routes the call to the C terminal 114 via connection 115, the PSTN 109 and connection 116, thereby completing the supplementary service.
It can be seen from this example that the information for originally routing the call is provided by the HLR 107, but that the logic decision of call forwarding, which is also a routing decision, is made by MSC2 113. If the called cellular subscriber 103 were to request that call forwarding be turned on or off, this would require updating not only the HLR 107, but also the visited MSC2 113. It would be preferable to have to update only one node.
In the second example, the prior art implementation of a "private numbering plan" service is illustrated. In this service, a calling subscriber places a call by using only a short number which the calling subscriber associates with the called subscriber. The calling subscriber relies on the service provider to substitute the full number for the called subscriber and correctly route the call. This supplementary service has been selected as an example because it illustrates the type of supplementary service which supplements the ability to originate a call. The prior art implementation of this supplementary service will now be described with reference to FIGS. 3 and 4.
In step 401, a calling mobile radio subscriber 301 (A=originating subscriber) calls a cellular subscriber 302 (B=called subscriber) using a short number out of a private numbering plan subscribed to and stored in the SCP 303.
In step 402, the MSC1 304 reads in its category store (which was updated via the MAP-interface 305 when the A subscriber roamed to the region of MSC1 304) that the calling mobile radio subscriber 301 has a "private numbering plan" stored in SCP 303. In response, the MSC1 304 routes the call to SSP 306 by way of connection 307, the PSTN 309, and connection 308. SSP 306 was selected because it is the switch associated with SCP 303.
In step 403, SSP 306 asks the SCP 303, via the interface 311 (the INAP), to translate the short number of B. In response, the SSP 306 gets back the actual number which may, for example, be a mobile radio number.
In step 404, SSP 306 routes the call to the MSC2 314 via connection 312, PSTN 309, and connection 313.
In step 405, MSC2 314 asks HLR 318, via the MAP-interface 319, about the location of the called cellular subscriber 302. In response, the HLR 318 provides the MSC2 314 with a roaming number for the called cellular subscriber 302. The MSC2 314 then routes the call to the called cellular subscriber 302 by way of connection 316 and MSC3 315, thereby completing the supplementary service.
It can be seen from this example that the information for routing the call to SSP 306 is provided in advance by the HLR 318 when it sends a category to MSC1. Furthermore, the number translation and information for routing the call back to the cellular network is provided by the SCP 303. Then, the routing of the call to the called cellular subscriber 302 is performed by HLR 318 giving a roaming number to MSC2 314. In addition to the disadvantage caused by unproductive loops (i.e., extra connections and points of decision-making in the routing of the connection), it is impossible for the calling subscriber 301 to change his private numbering using his mobile terminal, because the required interface is not defined.